**2. Background**

The "Birth of Nanotechnology" was the title used by David Thompson [19] on his article acknowledging Michael Faraday's synthesis of gold nanoparticles in 1857. What Faraday called "Colloidal Ruby Gold" [20] was, in fact, a solution of dispersed GNPs so small that no microscope of that time was able to observe them. It wasn't until 1985 that Turkevich et al. [21] used an electron microscope to corroborate that Faraday's ruby gold was formed by GNPs with an average size of 6 ± 2 nm. Separately, in 1967 Werner Stöber et al. developed a method of synthesizing silica spheres in the micron size range [22] to be used especially in the medical field due to its known cytotoxicity, and in 1998 they were used by Naomi Halas et al. as the templates of GNS [23].

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**Figure 1.**

*of reaction, and (d) at 2 h of reaction.*

*A Simple Way to Produce Gold Nanoshells for Cancer Therapy*

Ethanol (100%), tetraethyl orthosilicate (TEOS) (98%), 3-aminopropyltriethoxysilane (APTES) (99%), trisodium citrate dihydrate, gold (III) chloride trihydrate (HAuCl4, 49%), formaldehyde (37%), and sodium borohydride

(NaBH4, 98%) were purchased from Sigma-Aldrich. Potassium carbonate (K2CO3, 99%) and ammonium hydroxide (28%) were purchased from J.T. Baker. All the

Images were obtained using the field-emission scanning electron microscope (SEM, JEOL JSM-7401F) and the transmission electron microscope (TEM, HT7700 Hitachi). For the ultraviolet-visible (UV-Vis) spectra, the Evolution 220 spectrophotometer UV-Vis (Thermo Scientific) was used. The FTIR spectra were obtained with an IRAffinity-1S Fourier transform infrared spectrophotometer (Shimadzu). The sample was irradiated with an 820 nm wavelength/3.1 mW laser (Multi-Channel Fiber-Coupled Laser Source, Thorlabs), and the infrared images were taken with a Noncontact Digital IR Thermometer (TrueIR Agilent Keysight U5855A). Measurement of

the particles and histograms were acquired with the Image J® software [24].

adding the TEOS to observe the evolution of the process.

**3.4 Functionalization of the silica spheres**

Silica particles were prepared by modifying the Stöber method [22]. About 50 ml of ethanol, 2.5 ml of deionized water, and 4.25 ml of ammonium hydroxide were magnetically stirred in an 80 ml glass flask for 5 min. Then, 0.75 ml of TEOS was added dropwise. The solution was heated at 40°C. Temperature and agitation were kept for 2 h. The color of the solution changed from transparent to opaque white approximately 10 min after adding the TEOS as shown in **Figure 1**. This time corresponds to the induction period needed to form the SiO2 nucleus from the concentration used of the TEOS monomer [25]. Samples were obtained at 30, 60, 90, and 120 min after

In order to create open links over the silica to attach the GNPs, the silica was functionalized with APTES on a 1 ml:1 μl silica/APTES volume ratio. About 50 ml

*Images of the synthesis of SiO2 particles: (a) right after adding TEOS, (b) at 10 min of reaction, (c) at 30 min* 

*DOI: http://dx.doi.org/10.5772/intechopen.82495*

solutions were prepared with deionized water.

**3. Experimental**

**3.2 Characterization**

**3.3 Preparation of silica spheres**

**3.1 Materials**
